In a wastewater treatment facility by an activated sludge process, while air is supplied to a treatment tank containing an activated sludge (aeration tank), wastewater to be biologically treated is supplied to the treatment tank, a microbial community forming an activated sludge and wastewater are contacted under the aerobic environment, a microbial community takes up nutrient components in wastewater, and proliferates, thereby, organic pollution in wastewater is decreased. Wastewater that flows out from the treatment tank is guided to a precipitation tank to settle a sludge, and is separated from treated water. In such a wastewater treatment process by an activated sludge process, many kinds of microbes are present together in the treatment tank, and they form a sludge flock, and are floated and suspended in water in the aeration tank in many cases.
In this kind of wastewater treatment facility, in order to perform treatment in the stable state for a long period of time, it is required to grasp and manage the physiological state of a microbial community present in the treatment tank.
An example of the case where the physiological state of a microbial community in the treatment tank is unsatisfactory includes the case where a sludge flock becomes bulky and cotton-like, reducing a difference in a specific gravity between water, consolidation property of the sludge flock is reduced in the precipitation tank, and bulking occurs, in which separation between treating water and the sludge flock becomes difficult. When this bulking is generated, since it becomes difficult to separate treated water and the activated sludge in the precipitation tank, an operation efficiency of the wastewater treatment facility is extremely reduced.
In order to prevent this bulking, it is necessary to precisely grasp the physiological state of a microbial community present in the treatment tank, and take any strategy so that a bulking causal bacterium such as a filamentous bacterium does not predominantly proliferate.
However, a method for determining the physiological state of a microbial community which is effective in rapidly and precisely determining the physiological state of a microbial community present in the treatment tank has not previously been established, and it was difficult to prevent inconvenience such as bulking etc. in advance.
As a method for determining the physiological state of a microbe, for example, the prior art described in Patent Documents 1 to 3 has hitherto been proposed.
Patent Document 1 discloses a method of staining-treating a specimen containing a microbe using a first fluorescent dye, a second fluorescent dye having a wavelength which is different from a wavelength of the first fluorescent dye, and a third fluorescent dye having a wavelength which is different from wavelengths of the first and second fluorescent dyes, measuring fluorescent light with flow cytometry or a laser scanning cytometer, and grasping, from the result, the cell number, the environmental polluting compound cleaning activity and the survival state of a microbe which can clean the environmental polluting compound in the specimen by degradation, dechlorination etc.
Patent Document 2 discloses a method for determining the physiological activity of a microbe, which includes trapping a microbe on a filtration membrane, culturing the microbe, and staining the microbe on the filtration membrane with a fluorescent staining solution which has been permeated from a lower surface side of the filtration membrane.
Patent Document 3 discloses a method for analyzing a cell cycle, which includes the steps of visualizing a cell nucleus, a step of visualizing a biological molecule which is specifically expressed in a specified cell cycle, and identifying a ratio of the specified cell cycle in a cell population utilizing numerical value data of the cell nucleus obtained by visualizing the cell nucleus, and numerical value data of the biological molecule obtained by visualizing the biological molecule.
In addition, as a method of controlling the step of activated sludge-type wastewater treating, Patent Document 4 discloses the step of controlling an aerobic activated sludge-type wastewater treating step, comprising measuring an amount of a fluorescently labeled microbe with flow cytometry by binding a microbe to a fluorescently labeled antibody to this microbe, or converting a fluorogen substrate by the specific metabolism ability of the microbe, in a typical sample from an activated sludge and/or an inlet of an activated sludge tank, upon continuous monitoring of an amount of one kind or several kinds of microbes, regarding the microbes which appear most frequently in an activated sludge and, at the same time, measuring a total amount of microbes present in the sample by scattered light and/or DNA staining, and monitoring an amount of the microbe by regulating an amount of one kind or several kinds of specified microbes and/or the growth condition of the microbes, in response to the thus obtained measured value.